To put some content here, go to Site Admin -> Appearance/Presentation -> Widgets -> Select "Left Sidebar" -> Click "Show" -> Click on "Add" on one of the widgets on the left side -> Click "Save changes" -> Done

To put some content here, go to Site Admin -> Appearance/Presentation -> Widgets -> Select "Right Sidebar" -> Click "Show" -> Click on "Add" on one of the widgets on the left side -> Click "Save changes" -> Done